Known timer circuits are not entirely satisfactory for the range of applications in which they are employed. For example, existing timer circuits are incapable of being programmed for fractional time delays. In addition, conventional timer circuits typically have long reset intervals.
To date, the most used advanced trigger modes in oscilloscopes are the Glitch or Pulse Width trigger modes, in which an input pulse is qualified as a trigger event based on its width as compared to one or more reference timers. The critical performance parameters for these trigger modes using a reference timer circuit are the minimum timer setting and the minimum timer reset interval. The increased demand for higher bit rates has driven the next generation of timer circuit requirements to be on the order of ten times faster than the present designs.
Examples of references relevant to addressing these problems can be found in the following U.S. Patent references: U.S. Pat. No. 6,515,550, U.S. Pat. No. 5,355,097, U.S. Publication 2008/0001677, and U.S. Publication 2006/0232346. However, each of these references suffers from one or more of the following disadvantages: slow circuit reset times and the inability to program the circuit for fractional time delays.
Thus, there exists a need for timer circuits that improve upon and advance the design of known timer circuits. Examples of new and useful timer circuits relevant to the needs existing in the field are discussed below.